Possible pause-before values:

Values

Comments

CSS

[time]

Expresses the pause in absolute
time units (seconds and milliseconds).

2

[percentage]

Refers to the inverse of the value of the
'speech-rate'
property. For example, if the speech-rate is
120 words per minute (i.e., a word takes half a second, or 500ms)
then a 'pause-before'
of 100% means a pause of 500 ms and a
'pause-before'
of 20% means 100ms.